cc: nine patch: add occlusion support

cc/layers/nine_patch_layer.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_LAYERS_NINE_PATCH_LAYER_H_
 #define CC_LAYERS_NINE_PATCH_LAYER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 24 matching lines @@
   // aperture is in the pixel space of the bitmap resource and refers to
   // the center patch of the ninepatch (which is unused in this
   // implementation). We split off eight rects surrounding it and stick them
   // on the edges of the layer. The corners are unscaled, the top and bottom
   // rects are x-stretched to fit, and the left and right rects are
   // y-stretched to fit.
   void SetAperture(const gfx::Rect& aperture);
   void SetFillCenter(bool fill_center);
   void SetNearestNeighbor(bool nearest_neighbor);
 
+  // |rect| is the space completely occluded by another layer in layer
+  // space. This can be used for example to occlude the entire window's
+  // content when drawing the shadow with a 9 patches layer.
+  void SetLayerOcclusion(const gfx::Rect& occlusion);
+
  private:
   NinePatchLayer();
   ~NinePatchLayer() override;
   std::unique_ptr<LayerImpl> CreateLayerImpl(LayerTreeImpl* tree_impl) override;
 
   gfx::Rect border_;
   bool fill_center_;
   bool nearest_neighbor_;
 
   // The transparent center region that shows the parent layer's contents in
   // image space.
   gfx::Rect image_aperture_;
 
+  // The occluded region in layer space set by SetLayerOcclusion. It is
+  // usually larger than |image_aperture_|.
+  gfx::Rect layer_occlusion_;
+
   DISALLOW_COPY_AND_ASSIGN(NinePatchLayer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_NINE_PATCH_LAYER_H_